Underground utility installations (such as sewer pipes, electrical cable conduits, and the like) have become increasingly complex. This increasing complexity often requires frequent access by construction or maintenance personnel in order to install new utilities or upgrade and maintain existing utilities. Since these utility installations are located underground, access to them is generally accomplished through an entrance hole set at ground level. Personnel typically descend through the entrance hole into a vertical access conduit that permits access to the utility installations. These access conduits are commonly referred to as “manholes.”
The entrance hole of the access conduit is usually closed with some type of cover, such as a manhole cover or grating. These manhole covers can be of different shapes and sizes (circular, rectangular, etc.) depending upon the degree of access required or the type of access conduit that is in use. To ensure safety, security, and durability, manhole covers are typically constructed of a rigid material, such as cast iron. As a result, the manhole covers can be very heavy and difficult to lift, and may pose a safety risk to personnel who attempt to remove a manhole cover for entry into an access conduit.
One particular problem associated with lifting manhole covers is the danger associated with gas build-up within the access conduit under certain circumstances. Removal of the manhole cover may cause ignition of the gas, resulting in an explosion. Any personnel who are in close proximity to the access conduit therefore face severe danger and the possibility of extreme injury. Accordingly, there is a need for an apparatus that provides efficient and convenient manhole cover removal and replacement and at the same time keeps personnel safe by allowing such removal and replacement to be performed by personnel from a sufficient distance from the manhole cover and access conduit. In particular, there is a need for an apparatus that may be used to remove and replace manhole covers.
The invention described herein is intended to addresses the above needs. In particular, it is an objective of the invention to provide an apparatus that facilitates the efficient and convenient removal and replacement of manhole covers. Another objective of the invention is to permit personnel to safely perform such removal and replacement from a sufficient distance from the manhole cover and the access conduit. To achieve these and other objectives, the invention provides a lifting apparatus that permits safe and convenient removal and replacement of a manhole cover.